Antiinertia mechanism for sliding doors



Sept. 22, 1953 w. ARMSTRONG 2,653,022

ANTIINERTIA MECHANISM FOR SLIDING DOORS Filed July a. 195i 4 shuts-sum;I

Sept. 22, 1953 w. ARMSTRONG 2,653,022

ANTIINERTIA MECHANISM FOR SLIDING DOORS Filed July 3, 1951 4Sheets-Sheet 2 Sept. 22, 1953 w, ARMSTRONG 2,653,022

ANTIINERTIA MECHANISM FOR SLIDING DOORS Filed July 3. 1951 4Sheets-Sheet 3 2,0037% 242 0 flaw/29 Sept. 22, 1953 w, ARMSTRONG2,653,022

ANTIINERTIA MECHANISM FOR SLIDING DOORS Filed July 5, 1951 4Sheets-Sheet 4 llllll" Patented Sept. 22, 1953 UNITED STATES PATENTOFFICE ANTIINERTIA MECHANISM FOR SLIDING DOORS 22 Claims.

This invention relates generally to sliding doors and more particularlyis concerned with a mechanism for compensating for the inertia ofsliding doors both at the time of stopping and starting the movementthereof.

The problems caused by inertia of sliding members such as doors orpanels is principally of importance in the case of installations wherethe sliding members are of great weight. For example, large commercialestablishments such as warehouses and other material storage andhandling places use large doors, both for securing ingress to and egressfrom the structure, and as well for maintaining a constant separationbetween various sections of the structure. The latter type of doors areusually of the horizontal sliding type and are known as fire doors, andtheir purpose of course is obvious.

In such sliding members, the larger the door, the more power is requiredto operate the same and the more desirable it is to have as littlefrictional resistance as possible. In such cases (but also to a lesserdegree in the smaller door installations), the inertia acquired by thedoors while moving is considerable, and unless otherwise prevented fromdoing so, the doors violently collide with one another during closing,or with the mechanical door stops during opening. Such collisionsbesides being annoyingly noisy, result in damage to the installation inmany ways such as for example: deformation and deterioration of thedoors, the door tracks and cables, the stop means; breakage of parts;and unusual wear on all parts. of equal importance are the commoneffects of the door wheels jumping out of or bet coming jammed in thetracks, delay caused by inoperativeness of the installation, and thebouncing of the sliding doors at the end of their intended extent oftravel. This latter mentioned difficulty results in the doors remainingpartially open or partially closed although they should be suddenly upto the normal speed at which it is intended that these doors move. Oncethe initial friction has been overcome the door will suddenly surgeforward giving rise to a great jerk whose deleterious effects are quitesimilar to those mentioned in connection with stopping the doors. Thereis a great strain placed upon the operating mechanism and apparatus, anddeformation, damage, and the like are also not uncommon results of suchjerking.

Many mechanisms heretofore have been devised for absorbing orcounteracting the inertia of such large bodies as described, both instarting and stopping the same, but none have been satisfactory. Suchdevices have included dashpot systems, springs, and friction brakes, butnone of these expedients has been successful to the best of myknowledge. In particular, none of these mechanisms has been useful bothin starting and stopping sliding doors, and none is positive acting, andgives uniform results irrespective of the temperature, humidity, andmany other variable conditions to which such installations aresubjected. None of these mechanisms used have enabled the door to bebrought to a gradual and positive stop at each end of its path oftravel.

The principal object of my invention is to provide a mechanism whichwill alleviate the difliculties and solve the problems set forth above.Specifically the principal object is to provide a .positive actingmechanism which will enable doors (or other sliding bodies) to startsmoothly and stop smoothly; which will enable such bodies to come to apositive yet smooth stop in the same position regardless of thetemperature, humidity, speed of travel, and age of the installation;which will not require the use of dash-pots, brakes, clutches, or bumpersprings.

Another object of the invention is to provide a mechanism for use as ananti-inertia device in connection with sliding bodies such asbi-parting, horizontally sliding doors, in which the doors will start orstop with substantially simple harmonic motion, although the doorstravel normally at a substantially constant velocity. The describedmotion is not intended as a limitation, but merely to state that thedoor motion in starting is at first very slow, then increases invelocity, until it reaches the velocity of the cable, with the reverseprocess occurring during the stopping movement of the doors.

Still another object of the invention is to provide a device of thecharacter described which comprises a mechanism capable of readily beinginstalled upon a movable door or panel for cooperation with arectilinearly moving chain or cable secured to the door and adapted tobe moved to open or close the door.

A further object of the invention is to provide a mechanism forabsorbing the initial jerk of a cable-actuated sliding door and forabsorbing the final sudden stop thereof by enabling the cable to moverelative to the door at the beginning and end of the path of movement ofthe door, but which automatically and positively will lock the cable orchain to the door during the constant velocity travel thereof along thesaid path between starting and stopping.

Still another object of the invention is to provide a device of thecharacter described Which is extremely simple and made up of a minimumof easily fabricated parts; in which there is substantially no wear onthe parts; in which no electrical or hydraulic elements are required;and which may be made extremely rugged and durable, yet be small involume of space occupied.

Many other objects of the invention will become apparent as a detaileddescription of the invention proceeds, in which I have described by wayof illustration and elucidation (and not by way of limitation),preferred embodiments of the invention to carefully set forth the mannerin which the invention is used and constructed to carry out the objectsof the invention.

In the figures in which like or similar parts are represented by thesame characters of reference throughout the several figures of thedrawings:

Fig. 1 is a front elevational view showing the principal components ofan installation of sliding doors having associated therewith anantiinertia device constructed in accordance with my invention, andshowing the doors in a closed condition.

Fig. 2 is a View similar to that of Fig. 1 but illustrating only part ofthe installation, and g showing the doors partially open,

Fig. 3 is an elevational view on an enlarged scale of the left hand endof the installation illustrated in Figs. 1 and 2, but with the doorsbeing fully open, and thus illustrating the left hand door and theanti-inertia mechanism secured thereto, the front cover plate of saidmechanism having been removed.

Fig. 4 is a sectional view taken generally along the line 4-4 of Fig. 3and in the indicated direction.

Fig. 5 is a sectional view taken through the anti-inertia device alongthe line 5-5 of Fig. 4 and in the indicated direction.

Fig. 6 is a sectional view taken generally along the line 6-5 of Fig. 1and in the indicated direction.

Fig. 7 is a sectional view taken along the line 1-1 of Fig. 3 and in theindicated direction.

Fig. 8 is an elevational view on an enlarged scale of the anti-inertiadevice as disposed in Fig. 2, the front cover having been removed toshow the constructional details thereof.

Fig. 9 is a sectional view taken through the anti-inertia device alongthe line 9--9 of Fig. 8 and in the indicated direction.

Fig. 10 is a sectional view taken through the roller and guide of Fig. 3along the line lB-IO and in the indicated direction.

Fig. 11 is a perspective view of the rotatable segment of theanti-inertia device.

Fig. 12 is a view similar to that of Fig. 3 but showing a simplifieddoor installation and a modified form of the invention.

Fig. 13 is a sectional view along the line l3--l3 of Fig. 12 and in theindicated direction.

Fig. 14 is a semi-diagrammatical elevational view of parts of a modifiedform of the invention.

As previously set forth, the invention is intended to prevent thejerking in starting the movement of a sliding body, and the shockoccurring through sudden stopping thereof. It is to be understood thatthe invention is applicable to doors, panels, wall sections, or anyother sliding body of relatively large mass, and that such bodies may bearranged to move horizontally or vertically. It is desired to point outthat the fact that the illustrated embodiment is associated with a pairof bi-parting, horizontally sliding doors is not intended to limit theinvention to such use, or even to use with a pair of doors. Themechanism is as equally suited for use with a single sliding door orother sliding body.

Considering now the particular construction illustrated there is shown awall partition having an opening which is adapted to be closed by a pairof bi-parting sliding doors. The doors run on tracks arranged above theopening and slide in opposite directions relative to each other. Adriving mechanism is provided to drive a cable or chain about sheaves orpulleys and having one of the sliding doors secured to one reach of theloop to move rectilinearly with the reach. when the loop is driven. Asecond loop is provided independently mounted, and having one doorsecured to one reach thereof and the second door secured to the secondreach thereof so that the doors are counter-acting. In the case ofvertically sliding doors, the doors would thus be counterbalancing.

The anti-inertia mechanism is associated with the door first driven bythe driving mechanism, although in a system of this kind the second doorcould as easily have the said mechanism associated therewith. Theconjoined ends forming the first driven loop (distinguished by thisdesignation from the second or counter-acting loop) meet at the placewhere the loop reach is secured to the first door. However, instead of aconventional securement, I provide a segment of a pulley, with the axisthereof perpendicular to the line of movement of the door, and with itsplane preferably (although not necessarily) parallel to the plane of thedoor. The free ends of the loop cross along one portion of theperipheral edge of the segment and are secured to the segment onopposite sides thereof, so that pulling the reach in one direction tendsto rotate the pulley segment so that the said peripheral edge tends torotate towards that direction; and pulling the reach in the otherdirection has the opposite effect.

The segment is associated with a camming mechanism in a manner to bedescribed in detail, which renders the segment non-rotatable during thetime the doors are travelling between their open and closed positions,so that the driven loop acts directly upon the first door. At the beginning and end of the path, the mechanism locking the segment againstrotation relative to the door and driven loop is rendered ineffective bymeans which is dependent upon the distance of the door from said means,so that the segment becomes capable of limited rotation at these times.Rotation of the segment is opposed by spring means, but said oppositionis readily overcome and is provided only to efiect recovery of thesegment to erect position in certain cases, as will be described. In thepreferred embodiment the spring is necessary only to keep the segmenterect and not to help it achieve that position. The effect of thesegment being able to rotate at the beginning and end of the movement ofthe door is as follows: in starting, the initial jerk of the loop willbe utilized in rotating the segment from a substantially free to alocked erect condition with respect to the door, but the lockedcondition is attained only when the door has moved away from itsposition of rest and has begun to travel at normal movement velocity,and hence the door will start slowly and smoothly to move as more andmore pulling power is made available to it; and in stopping, the inertiaof the moving mass is first dissipated when the segment begins to rotateso that the speed of the drive cable may remain constant until the endof the movement, but the stopping effect thereof is felt by the door ata gradually increasing and smooth rate which may be substantially simpleharmonic in nature. The travel of the cable in stopping will be wellbeyond the ordinary point of securement thereof to the door, but thisresults in a rotation of the segment to an unlocked condition in whichit remains until after the door is started from rest position once more.It is pointed out that the locked and unlocked positions referred to arethe erect and rotated positions of the segment relative to the door. Itshould be remembered that in its rotated positions, the segment causesthe door to be substantially locked against move ment relative to thewall.

Referring now to the constructional details illustrated, the referencecharacter designates generally a wall of any suitable constructionhaving a conventional rectangular opening 2| which is closed off by apair of biparting horizontally sliding doors. The doors are designatedas'the first door 22 shown on the left in Fig. 1, and the second door 23shown on the right in Fig. 1. Each of the doors is formed in anysuitablefashion well-known in the art, such as for example, as shown in'Fig. '7,wherein the door 22 has a rectangular sheet metal panel 24 reinforcedand framed by angle iron'members 25 suitably bolted in assembly by bolts25. Obviously the door could be formed of wood, or laminated withfireproof material or the like. It should be appreciated that the doors22 and 23 will have considerable mass.

Each of the doors 22 and 23 has a pair of hangers (see Fig. 7) having across bar 3| at the bottom thereof bolted as at 32 to the upper edges ofthe respective doors, and having a stub shaft 33 journalled in the upperend thereof. The stub shaft has a pair of freely rotatable wheels 34mounted thereon on opposite ends with the hanger secured in the centerbetween the wheels. A box track 35 extends along the upper edge of theopening 2|, being secured to the wall 20 by suitable brackets 36 boltedto the wall as at 31 and secured to the box track as for example bywelding, as shown at 38. The box track 35 has a generally rectangularcross-sectional configuration with a longitudinal slot 40 in the bottomthereof of a width sufficient freely to accommodate the hanger 30. Thewheels 34 are thus disposed internally of the box track and ride uponthe bottom thereof.

Three of the brackets 36 are illustrated in the drawings, and theirconstruction is identical, except that the two outer placed of thesebrackets each have a sprocket wheel 4| journalled upon 6 a stub shaft 42secured to a socket 43 which in turn is mounted to the rear of thebrackets. A chain or cable 44- is engaged in an endless loop over thesesprocket wheels 4| having an upper reach 45 and a lower reach 46. Eachdoor has an extension as shown at 41 and 48 in Fig. 1, secured at theupper meeting corners of the respective doors, and the extensions arerespectively secured to the reaches 45 and 46 to move therewith.Obviously, when the first door 22 moves to the left it causes the seconddoor 23 to counter-act and move to the right, and vice versa.

The box track 35 has a bracket 50 bolted to the front thereof at theleft hand end thereof as viewed in Fig. 1 to provide bearing support fora shaft 5| as shown in Fig. 4. Shims 52 may be provided for adequatejournal surface. The shaft 5| extends through the box track 35 and outthe rear thereof. To the front of the shaft there is mounted a sprocketwheel 54 and to the rear of the shaft is secured another sprocket wheel55. There is a bracket 56 and sprocket wheel 51 similar to bracket 50and wheel 54 respectively, secured to the right hand end of the boxtrack 35, but having no additional wheel similar to 55. A flexibledriving element is looped over the two wheels 54 and 51, and the firstdoor 22 is secured to the bottom reach of this element. The element canbe any cable, or chain or belt, but in the illustrated embodiment, it isconveniently and economically made up of a length of sprocket chain 60on each end of the loop to engage the respective sprocket wheels, andgive positive drive, and lengths of flexible cable, BI and 62 secured tothe chain ends as for example at 63.

Adjacent to the left hand end of the box track 35 there is provided asuitably supported platform secured by bracket H to the wall 29. Theplatform 10 supports the driving means for moving the doors. Sameincludes an electric motor 12 having a shaft 13 driving a worm I4 andpinion 15 in the gear reduction unit 15, Obviously any suitable speedreducing means and prime driver can be used. Likewise, it has not beendeemed necessary to illustrate further and describe the shaft couplingsand conventional details. A suitable brake mechanism is shownsymbolically at T1. The pinion l5 drives a sprocket wheel 78 and asprocket chain i9 engages over wheel 18 and wheel 55. When the motor 12is energized, the driving mechanism will rotate the loop includingcables 6| and 62 thereby sliding the door 22 right or left as the casemay be, since the door is secured to cable 62 as will be explained.

Electrical controls and connections are not shown since same are capableof assuming many different forms.

As thus far described, the installation is substantially the same as anyconventional sliding door arrangement which utilizes the same or similarfeatures. There is no provision, as thus far described, which willprevent the doors from crashing together upon closing or crashingagainst their respective stops upon opening.

There is no provision for preventing starting jerk from occurring as thedoors pass from rest to moving condition. More important, there is noprovision for enabling the doors gradually to come to a stop from theirmoving condition during the last phases of movement and coming to restat substantially the identical position upon every cycle of movementthereof. These things are accomplished only by the invention which willhereinafter be described.

Mounted in the upper left hand corner of the door 22 is a mechanism,designated generally by the reference character 80 which will enable theaccomplishment of the advantages mentioned. These are a cushioning ofthe doors during stopping, the gradual increasing of the velocity of thedoors during starting to prevent jerking, the stopping of the doors atthe end of travel at predetermined points. The anti-inertia device 80 isbest illustrated in Figs. 3, 5, 8, and 9. The movable parts of saiddevice are mounted between front and rear generally triangular shapedplates SI and 82, the rear plate 8| being secured to the front of thedoor 24 in any suitable manner such as by welding as shown at 84 toassure that the device will move with the door. It is emphasized thatthe only connection between both doors and the lower cable 62 isachieved by way of the device 80 and no external stop members areprovided for the doors. The plates 8| and 82 are spaced one from theother by spacers 86 bolted at the lower corners thereof.

In order to provide for mounting of the device 80 upon the door 22 theupper angle iron 25 may be cut away as at 89 and the welds 84 may secureangle brackets 90 to the rear of the plate 82 which brackets may bebolted as at iii to the angle iron 25. At the lower end of the plate 82there may be provided a nut 92 welded as at 93 to the rear thereof, forreceiving a bolt 94 therein. A stand-oil spacer 95 is provided throughwhich the bolt 94 secures the lower end of the device 80 to the door 22.

The rear plate 82 has mounted thereon a rotatable pulley segment 81having a grooved upper edge 88 (see Fig. 11) curved about the center ofrotation of the said segment. The segment 81 is generally of keystoneformation and is pivoted upon a bolt 91 mounted on a bushing 98 which isinserted in the rear plate 82. A suitable anti-friction washer 99 may beprovided. As will be noted the lower cable member 52 is actually formedof two parts, each of which is crossed about the keystone-shaped pulleysegment and secured thereto. end designated 62 which passes over thegrooved edge 88 from left to right as viewed in Figs. 8 and 11, andthence passes down the right hand edge IIlI of the segment 81 and roundthe bottom The end desigedge I02 where it terminates. nated 62" passesover the pulley edge 88 from right to left, down the left side I03, andaround to the bottom 422 where it also terminates. Both ends are securedto the bottom edge I02 by any suitable means such as clamp washers Iheld in place by simple screws I05. An other securement means issuitable. The ends 62' and 62" are secured with the cable 62 taut bymeans of turnbuckles (not shown) for example.

As thus far described, it will be appreciated that if the keystoneshaped pulley segment 8! is freely rotatable, but limited in its extentof rotation, say through thirty Or forty degrees (not considering anyother part of the mechanism which will be described) then, from anupright position of said segment, if the cable 62 is moved either rightor left, before the door 24 will commence to move, the segment 81 mustrotate through the extent available.

This rotation of the segment relative to the door, so that there ismovement of the cable relative to the door prior to movement of thedoor, is an important principle used in achieving the results alluded toherein. Obviously there is Thus, there is one means provided to controlthe rotation or absence of rotation of the pulley segment which will nowbe described.

I provide a pair of cam members III! and III disposed between thesegment 81 and one of the plates. In the embodiment illustrated the cammembers are adapted for movement between the segment 81 and the frontplate III. The cam members are pivotally mounted at the top of thedevice at H2 and H3 respectively. Each member has certain cam ways whichwill be described, for cooperation with the pulley segment 81. As viewedin Fig. 8, the major portions of the cam members extend downward andover the pulley segment. It should be appreciated that the pulleysegment could be mounted on the front plate and the cam members mountedbetween it and the rear plate, but this arrangement is obvious, and neednot further be discussed, especially since it makes no diiference in theoperation of the device.

The cam member III] is intended to rotate about its pivot I I2 from itserected position as shown in Fig. 8 to the position shown in Fig. 3 in acounter-clockwise direction at the left hand end of the path of movementof the door 22. Likewise the cam member II I is intended to rotate fromthe position shown in Fig. 8 to a position similar to that of cam memberIII] in Fig. 3, albeit a mirror position thereof and not shown in thedrawings, when the door 22 has reached its extreme right hand end of itspath of movement. During the rotation of the respective cam members asdescribed there may be a slight movement of the opposite cam which is ofno importance. In the preferred embodiment first described, the pivotalmovements of the cam members I I0 and III at the ends of the path of thedoor 22 is positive and forced, both while the door is approaching thatend and leaving that end, but in another embodiment which will bedescribed, recovery of the respective cam members to erect position iseffected by spring biasing means. Thus, in the latter referred tovariation of the structure, the cam members III] and III ar biased torotate in clockwise and counter-clockwise directions respectively.

Referring now to Figs. 3 and 8, a coiled spring H4 is shown connectedbetween eyes H5 and I I6 of the respective cam members. In the preferredembodiment, this spring H4 is a mere refinement and intended for holdingthe cam members I I0 and I I I erect and firm against play. In themodified form (i. e., where the paths of movement of the cams are notpositively confined and determined by certain track means in a mannerwhich will be described) the said spring II4 would serve as means forbiasing the cam members III] and III to recover their erect positionsafter the door has left a position of rest. This will b explained fullyhereinafter in connection with Fig. 14. Other biasing means will also bedescribed.

Considering now the left hand cam member IIO, there is provided a camway therein in the form of a slot II'I whose shape is irregular. Theslot has three parts, all connected together in such a manner that a camcan pass smoothly throughout the entire extent of the slot II'I. Thereis an upper arcuate portion II8 whose center of curvature is the pivot91 of the pulley segment 81 when the device 80 is in the condition shownin Fig. 8. At its lower end, the upper arcuate portion II8 connects witha rectilinear portion I19 which extends at an oblique angle therefromdownwardly and to the left, the juncture between the two portions beingdesignated I20. The lower end of the portion H9 connects with a lowerarcuate portion I2I Whose center of curvature is generally in thevicinity of the center of the pulley segment 81. Actually, in thecircumstance that the lower arcuate portion I2I is in use, the mechanismis so arranged that the center of curvature of said arcuate portion I2Iis the pivot 91, as illustrated in Fig. 3.

The pulley segment 8'! is provided on its front surfac with dowels orpins I22 and I23, the first of which is engaged in the slot Ill and actsas a cam therefor. The dowel I22 is held against the pulley segment 81by the screw I24.

It will be noted that the cam members III} and III are of irregularshape, and it is desired to point out that the shape is immaterial solong as the paths for movement of the dowels or pins I22 and I23 areprovided.

Referring now to the right hand cam member III and its pin or cam I23,the construction thereof is identical to that described for the cam.member II!) and its pin I22. Thus there is a slot I25, upper arcuateportion I26, juncture I2'I, rectilinear portion I28, lower arcuateportion I29. and the pin I23 is held in place by the screw I30. Thedifference between the members III? and III is that they each face inopposite directions from one another.

The additional constructional features of the device 80 will for themoment be disregarded, and the operation of that part thus for describedwill be set forth in detail. In Fig. 8 there is illustrated a conditionin which the door 22 is moving, either to the right or to the left. Inother words, its velocity is equal to the velocity at which the cable 62is being moved. The tendency of the cable to rotate the segment 81 isresisted because the cam pins I22 and I23 are positioned in thejunctures I20 and I2! respectively. The cam members III] and III in thisposition will be considered erect. Tendency of the pulley segment 81 torotate in a clockwise direction is opposed by the cam pin I23 bearingagainst the lower edge of the juncture I21. Since the movement whichwould be required of the cam pin I23 is at right angles to the radius ofthe upper arcuate portion I26 from the pivot 91 to the pin I23, and theline of this movement practically passes through the pivot I I3 of thecam member I I I, there can be no moment given to the cam. In addition,the bias of the spring II4, although 'quite small, is suflicienteffectively to lock the cam member II, and hence the pulley segment 81against movement.

Summarizing, in the condition illustrated in Fig. 8, the device BI] islocked against rotative movement, and the cable 62 is secured to thedoor and moves therewith. This situation prevails while the door isbetween its limits of movement, 1. e., when the cable 62 is being drivenat a constant velocity.

It becomes apparent, that in order to unlock the anti-inertia device, itwill be required to swing the cam members III] or III inwardly, i. e.,against the bias of the spring II4. Two expedients are illustrated foraccomplishing this function, one being illustrated in the embodiment ofFigs. 1 to 10 inclusive and the modified form of Figs. 12 and 13, andthe other being illustrated in Fig. 14, the keystone shaped pulleysegment 81 is substantially the same in both cases. The modified form ofFigs. 12 and 13, a1-

though slightly different, operate on the same principles as theembodiment of Figs. 1 to 10.

In order to unlock the anti-inertia device 80, i. e., render sameoperative, means must be provided which operate as the door 24approaches a position of rest. Furthermore, the same or other means mustbe provided which render the device operable as the door leaves itsposition of rest. To accomplish these functions, I provide the cammembers I It and III with extensions I40 and MI respectively, in theform of integrally formed elongate arms extending upwardly and to theright or left as the case may be. The ends of the extensions areprovided with free rollers I42 and I43 respectively mounted thereon inany suitable fashion. The box track 35 at the left hand end thereof isprovided with a pair of metal strips I44 and I45 Welded or otherwisesecured to the front member of the box track and arranged parallel oneto the other. They form a channel or track I46 which slants downwardlyand to the left as viewed in Fig. 3 in the path of the roller I42 as itmoves to the left with the door. Since the roller I42 is movingrectilinearly when the door 24 is moving to the left, when said rollerI42 enters the track I46 it will be positively guided downwardly and tothe left as the door 22 continues to move to the left. This movementwill now rotate the cam member III] in a counterclockwise direction.This movement is against the bias of the spring II4 which, as has beenexplained, is not essential to the operation of the device. As thisoccurs, the anti-inertia device becomes unlocked from the door, i. e.,the pulley segment 81 becomes free to rotate. The inertia of the door 22is cushioned as the door operates the limit switch I41, and comes to astop.

This action occurs in two steps which occur either simultaneously or inoverlapped relation. The rotation of cam member I I0 first causes thecam pin I22 to leave the juncture I20 and begin to follow the straightslot portion I IS. The pulley segment 8'! will begin to rotate in acounterclockwise direction about the pivot 9'I, but not a great deal. Atthe same time, the opposite. cam pin I23 begins to travel up the arcuateportion I26. The cable 62 now begins to move a slight amount to the leftrelative to the door 22. Since the cable is travelling at a constantvelocity, this relative movement gives rise to a slowing down of thedoor. The cam pin I22 continues to move-down the slot I I9, slowing thedoors velocity. The relative movement between the cable 62 and the doorcontinues as the pulley segment rotates giving rise to this phenomenon.Obviously, since the portion H9 is straight, the rotation of the cammember III! at a constant speed will increase the speed of rotation ofthe pulley segment 81 until the end of the portion H9 is reached. Thearm IIEl stops rotating at this point, although the segment 81 is freeto rotate. The instant that the cam pin I22 enters the lower arcuateslot I2I the arm III] cannot rotate because if it does the pin I22 mustmove in a direction perpendicular to a line drawn from the pivot pointII2 through the pin. The only time that this was possible was when thepin I22 was in the rectilinear portion I I9 of the cam way 1. Therefore,since the pivot point H2 is fixed relative to the door 22, the fact thatthe cam member I It cannot move when the pin I22 enters the slot I2Iforces the door positively to stop. By adjustment of the relativearrangement of the various parts, i. e., the positions of the device 80,the track 46, and the door 22 with respect to the opening 2I, theprecise position at which the door is to stop can be determined.

Furthermore, this position can be kept at the identical point for everycycle of door movement within the limits afforded by the play of themechanism. It is a relatively simple matter to have this point remainwithin a one-sixteenth of an inch variation for the larger type of firedoor installation.

After the door has stopped moving to the left, as is the situation inFig. 3, the segment 81 is still free to rotate, and in this case, thecam pin I22 rides down the lower arcuate slot I2I while the opposite campin I23 rides up the slot I26. This permits the cable 62 to continuemoving for a short distance while the motor 12 is braked to a stop. Thelimit switch de-energizing the motor 12 may be adjusted to shut off thepower just before the roller 42 enters the track I46 or may be set anytime before or after. ferred that the cable 62 come to rest before thepin I22 engages the termination of the arcuate portion I2I. It will beobvious, however, that regardless of where the pin I22 stops itsmovement relative to the arcuate portion I2I, the

door 22 will stop its movement at the same point relative to the opening2I. This makes for perfeet, positive, and, gradual stopping regardlessof many conditions which would affect other methods of stopping thedoors, such as humidity,

temperature, frictional variations, play in the driving mechanism, etc.

It should be appreciated that the device 80 need not have two cammembers to give the desired results, considering only one end of thetravel of the door. In other words, the cam member I I and pin I22 actto cushion the door 22 at the left end of its travel and absorb thejerking when the door starts off from left rest position toward theright. door were cushioned in some other fashion and jerking preventedin another way, the cam member III and pin I23 would be unnecessary andcould be eliminated. In their place there could be some simple stopmechanism to preventclockwise rotation, of segment 81. Since, however,it is best to provide anti-inertia means at both ends of the travelpath, the second cam member is needed. Likewise, for a single actionantiinertia device, the upper arcuate slots H8 and I26 would not berequired.

Referring once more to Fig. 3, let us presume that the cam pin I22 hasmoved to a halt in the lower arcuate portion HI, and the cam pin I23 hasmoved adjacent the upper end of the arcuate portion I26 of the slot I25.rest at the left end of its travel path. When the motor 12 is energized,it reaches constant speed almost at once. This would normally cause thecable 62 to start the door 22 moving to the right with a jerk. However,because of the antiinertia device 80-, the inertia of the door is notpermitted to oppose movement of the cable 62 to the right.

When the cable begins to move, it starts-rotating the pulley segment 81in a clockwise direction. First the pin I22 travels up the arcuate slotportion I2 Iv without affecting the cam member I I0 and without movingthe door. Next the cam pin I22 enters the slot portion I I9 and. beginsto rotate the arm III] clockwise about the pivot II2, pulling the rollerI42 up the track I46 and thus moving the door forward. Asthe arm IIOmoves from its position above described to. that of Fig. 8, the segment81 rotates at a decreasing rate It is pre- 1 If the right hand end ofthe w The door 22 is at 12 of rotation until it stops atv the positionshown in Fig. 8, and being unable to travel further, locks the cable 62to the door 22. Thus the speed of the door 22 has gradually increaseduntil it is equal to the speed of the cable 62.

Obviously the same operations described for stopping the door occur,albeit in an opposite direction, when the door reaches the right handend of its travel path. The roller I43 enters track I50 formed betweenstrips I5I and I52 to cushion the dOOr 22. Jerking during starting alsois prevented in the manner described. In this last mentioned case, thesegment 81 rotates counterclockwise.

The parts of the anti-inertia device referred to as cam members I I0 andI I I have been described as having the extensions I and MI forcooperation with the tracks I46 and I to rotate the respective cammembers in the manner set forth above. Obviously, any means capable ofcausing the rotation is equivalent. For example, in Fig. 14 I havediagrammatically shown a cam member 2H) pivoted at 2I2 and having abiasing spring 2 I4 tending to rotate same in a clockwise direction. Theremainder of the anti-inertia device need not be illustrated since itsconstruction is obviously the same as the device 80 (except that theopposite cam member is like 2 I0). Note that the extensions I40 and MIhave no counterpart here. Instead, there is a fixed member 240 which issecured to a. wall or the like and which is aligned with the cam member2 I 0 so that when the door carrying the cam member 2 I0 approaches itsposition of rest, the end of the member 240, which may be provided witha roller 24I, engages the edge of the cam member 2H) and rotates thesame in a counter-clockwise direction. In this variation of theinvention, the biasing spring 2I4 is essential in order to forcerecovery of the cam 2 I0 to erect position when starting to move thedoor to the right.

Another manner of causing the desired rotation of the cam member isillustrated in Figs. 12 and 13. Here are shown a simple metal rail Isecured to a. wall I6I by brackets I62, a conventional door I63 havinghangers IE4 mounting roller wheels, one of which is shown at I65 forrolling the door along the rail, and a driven sprocket wheel I66 andsprocket chain I51 and cable I68, the drive mechanism of which is. nodifferent from that previously described. An anti-inertia mechanism I10is secured to the door I63 and its construction is substantially thesame as the device with the exception of the absence of the extensionarms I40 and MI. Instead, the cam member I1I (which is the equivalent ofthe cam member IIO) has an elongate push rod I12 pivotally mountedthereto at I 13. The bias provided in the device 80 by the spring H4 isnow provided by a coil spring. I14 secured to the rod at I15 and thedoor IE3 at I16 and tending to pull the rod. to the left as viewedinFig. 12. Again, in this version, because of the track I82, the springbias is not essential. At. the upper left hand corner of the door I63 Ihave provided a support plate I 11. to which is pivotally mounted acrank arm I18 rotatable about the pivot I19. The right arm is pivotallymounted at I80 to. the left hand end of the push rod I12 while the leftarm has a roller II which is adapted to enter and slide down the trackI82 formed between the strips I83 and I84 secured to the bracket I85,which in turn is fixed to the rail I60.

The operation of the structure of Figs. 12 and 1-3 is identical to thatof the structure previously "13 described and hence no further detailsneedbe set forth. The push rod and crank arm structure are duplicated onthe right hand side of the door I63, of which only a part of the pushrod 186 is seen in Fig. 12.

It is believed that the invention has been set forth with suflicientclarity and detail to enable one skilled in the art to which sameappertains to construct and operate practical embodiments thereof. Aspointed out, the device operates effectively in connection with anylarge moving mass, and it is unnecessary that same consist ofhorizontally sliding articles, but can be movable either vertically orobliquely. Likewise, many details can easily be varied both as tolocation and dimension without in any way departing from the spirit ofthe invention or the scope thereof as defined by the appended claims.

I claim:

1. An anti-inertia device for an article slidable along a path relativeto a fixed structure, said article being driven by a flexible drivemember linearly movable relative to the fixed structure along a pathsubstantially parallel with said first path, a mechanical coup-lingbetween the drive member and the article so that said article is adaptedto move with the drive member, said coupling being normally locked whilesaid article is moving along said path, but becoming unlocked when saidarticle is at an end of its path to permit limited relative movementbetween said article and drive member, said coupling comprising a memberpivotally mounted upon said article and having said drive memberconnected thereto and tending to rotate the same, means preventingrotation of said pivotal member in one direction, means in the path ofsaid pivotal member preventing rotation in the other direction butremovable therefrom when said article is adjacent and at said path end.7

2. An anti-inertia device for an article slidable along a path relativeto ,a fixed structure, said article being driven by a flexible drivemember linearly movable relative to the fixed structure along a pathsubstantially parallel with said first 'path, a mechanical couplingbetween the drive member and the article so that said article is adaptedto move with the drive member, said coupling being normally locked whilesaid article =is moving along said path, but becoming unlocked when saidarticle is at an end of its path to permit limited relative movementbetween said article "and drive member, said coupling comprising amember pivotally mounted upon said article and :having said drive memberconnected thereto and tending to rotate the pivotal member, meanspreventing rotation of said pivota1 member in one direction, means inthe path of said pivotal member preventing rotation in the otherdirection but removable therefrom when said article is adjacent and atsaid path end, and means causing ;limited rotation of said pivotalmember when said second mentioned rotation preventing means has beenremoved.

3. An anti-inertia device for an article slidable along a path relativeto a fixed structure, said ble during a portion of the move-mentor saidarticle along said path, and means rendering said pulley rotatableduring other portions of movement along said path.

4. An anti-inertia device for an article slidable along a path relativeto a fixed structure, said article being driven by a flexible drivemember linearly movable relative to the fixed structure along a pathsubstantially parallel with said first path, a pulley mounted with itspivot fixed to said article, said drive member making at least a partialloop about said pulley whereby to be effectively tangential thereto andcapable of rotating the same whilst moving relative to the article, apulley control member carried by said article engaged with said pulleyfor preventing its rotation in one direction during movement of thearticle along a portion of said path, and means fixed relative to saidstructure adapted'to be engaged with said pulley control member, duringanother portion of said path to move said control member relative tosaid pulley rotating said pulley thereby causing relative motion betweensaid pulley and drive member and absorbing inertia.

5. An anti-inertia device for an article slidable along a path relativeto a fixed structure, said article being driven by a flexible drivemember linearly movable relative to the fixed structure along a pathsubstantially parallel with said first path, a pulley mounted with itspivot fixed to said article, said drive member making at least a partialloop about said pulley whereby to be effectively tangential thereto andcapable of rotating the same Whilst moving relative to the article,pulley control member carried by said article engaged with said pulleyfor preventing its rotation in one direction during movement of thearticle along a portion of said path, and means fixed relative to saidstructure adapted to be engaged with said pulley control member duringanother portion of said path to move said control member relative tosaid pulley rotating said pulley thereby causing relative motion betweensaid pulley and drive member and absorbing inertia,

' .said pulley and control member having cooperating cam and followermeans defining said relative movement along a path permitting limitedmovement of said pulley control member, whereby said member will causesaid article to stop moving simultaneously with cessation of movement ofsaid pulley control member.

6. An anti-inertia device for an article slidable along a path relativeto a fixed structure, said article being driven by a flexible drivemember linearly movable relative to the fixed structure along a pathsubstantially parallel with said first path, a pulley mounted with itspivot fixed to said article, said drive member making at least a partialloop about said pulley whereby to be effectively tangential thereto andcapable of rotating the same whilst moving relative to the article, apulley control member carried by said article engaged with said pulleyfor preventing its rotation in one direction during'movementof thearticle along a. portion of said path, and means fixed relative to saidstructure adapted to be engaged with said pulley control member duringanother portion of said path to move said control member relative tosaid pulley rotating said pulley thereby causing relative motion betweensaid pulley and drive member and absorbing inertia, said pulley andcontrol member having cooperating cam and follower means defining saidrelative movement along a path permitting limited movement of saidpulley control member,

whereby said member will cause said article to stop movingsimultaneously with cessation of movement of said pulley control member,and also permitting additional movement of said pulley after thecessation of movement of said pulley control member and article, therebyenabling additional relative movement between the drive member and thearticle.

7. An anti-inertia device for a large slidable door moving relative to afixed structure and having a flexible drive member adapted to be movedparallel with the door and have the door attached thereto, comprising apulley member pivoted on the door, the drive member making at least apartial loop around the pulley and tending to rotate the same thereby tocause relative movement between door and drive member, a cam memberpivotally mounted on the door with the pivot thereof spaced from thepulley pivot and having a connection with said pulley, said connectionincluding a follower and a defined path for the follower, said cammember and pulley being arranged during normal movement of the door withthe follower and path disposed to prevent rotation of the pulley andhence relative movement between door and drive member, but with thefollower movable along said defined path when the door approaches theend 'of its travel to cause the pulley to rotate in a direction whichwould carry the drive member ahead of the door thereby slowing down thedoor.

8. An anti-inertia device for a large slidable door moving relative to afixed structure and having a flexible drive member adapted to be movedparallel with the door and have the door attached thereto, comprising apulley member pivoted on the door, the drive member making at least apartial loop around the pulley and tending to rotate the same thereby tocause relai tive movement between door and drive member, a cam memberpivotally mounted on the door with the pivot thereof spaced from thepulley pivot and having a connection with said pulley, said connectionincluding a follower and a defined path for the follower, said cammember and pulley being arranged during normal movement of the door withthe follower and path disposed to prevent rotation of the pulley andhence relative movement between door and drive member, but with thefollower movable along said defined path when the door approaches theend of its travel to cause the pulley to rotate in a direction whichwould carry the drive member ahead of the door thereby slowing down thedoor, the said structure and cam member having means cooperativelyengaging as the said door approaches said end and rotating same alimited extent and said follower moving along said path during saidrotation in an are having a pulley pivot at its center while moving awayfrom the cam member pivot.

'9. An anti-inertia device for a large slidable door moving relative toa fixed structure and having a flexible drive member adapted to be movedparallel with the door and have the door attached thereto, comprising apulley member pivoted on the door, the drive member making at least a:partial loop around the pulley and tending to rotate the same therebyto cause relative movement between door and drive member, a cam memberpivotally mounted on the door with the pivotthereof spaced from the:pulley pivot and having a connection with said pulley, said connectionincluding a follower and a defined path for the follower, said cammember and pulley being arranged during normal movement of the door withthe follower and path disposed to prevent rotation of the pulley andhence relative movement between door and drive member, but with thefollower movable along said defined path when the door approaches theend of its travel to cause the pulley to rotate in a direction whichwould carry the drive member ahead of the door thereby slowing down thedoor, the said structure and cam member having means cooperativelyengaging as the said door approaches said end and rotating same alimited extent and said follower moving along said path during saidrotation in an are having the pulley pivot as its center while movingaway from the cam member pivot, said path including an extension engagedby the follower substantially at right angles with a line drawn throughthe follower and the cam member pivot whereby the cam member isprevented from further movement and the door is thus stopped.

10. An anti-inertia device for a large slidable door moving relative toa fixed structure and having a flexible drive member adapted to be movedparallel with the door and have the door attached thereto, comprising apulley member pivoted on the door, the drive member making at least apartial loop around the pulley and tending to rotate the same thereby tocause relative movement between door and drive member, a cam memberpivotally mounted on the door with the pivot thereof spaced from thepulley pivot and having a connection with said pulley, said connectionincluding a follower and a defined path for the follower, said cammember and pulley being arranged during normal movement of the door withthe follower and path disposed to prevent rotation of the pulley andhence relative movement between door and drive member, but with thefollower movable along said defined path when the door approaches theend of its travel to cause the pulley to rotate in a direction whichwould carry the drive member ahead of the door thereby slowing down thedoor, the said structure and cam member having means cooperativelyengaging as the said door approaches said end and rotating same alimited extent and said follower moving along said path during saidrotation in an are having the pulley pivot as its center while movingaway from the cam member pivot, said path including an extension engagedby the follower substantially at right angles with a line drawn throughthe follower and the cam member pivot whereby the cam member isprevented from further movement and the door is thus stopped, saidextension also defining an are about the pulley pivot so that althoughthe door has stopped the drive member may continue to move relative tothe same.

11. A structure as defined in claim 8 in which the cam member isprovided with means biasing same against said rotation.

12. A structure as defined in claim 8 in which the means comprises atrack and track rider normally disengaged but movable relative one tothe other along the way defined by the track when the door is less thana predetermined distance from said structure.

13. A structure as defined in claim 12 in which the track is carried bythe structure and the rider consists of a roller carried by said cammember.

'14. A-stnucture as definedin claim 12 in which "17 the track isattached to said structure and there is provided a crank arm having saidrider thereon and having linked connection with said cam member.

15. A structure as defined in claim 7 in which said door has a secondcam member arranged opposite the first cam member and having theidentical construction although arranged to be operated in the mannerdescribed in said claim for said first cam member, but only when thedoor approaches the end of its travel opposite to that defined in saidclaim.

16. A structure as defined in claim 8 in which there is a second cammember identical and opposite having identical and opposite connectionand adapted to slow the door down when moving in the opposite direction,and the structure and said second member have identical cooperatingmeans operative as the door approaches the end opposite that defined insaid claim.

17. A structure as defined in claim 9 in which there is provided asecond identical and opposite cam, and having a second identical andopposite connection with said pulley for slowing the door down whenmoving in the opposite direction, each path including an arcuate portionat the end opposite said extension arranged to accommodate movement ofits follower while the pulley is rotating to carry the opposite followertowards the extension of the opposite path.

18. An anti-inertia device for a large slidable door moving relative toa fixed structure and having a flexible drive member adapted to be movedparallel with the door and have the door attached thereto, comprising apulley member pivoted on the door, the drive member making at least apartial loop around the pulley and tending to rotate the same thereby tocause relative movement between door and drive member, a cam memberpivotally mounted on the door with the pivot thereof spaced from thepulley pivot and having a connection with said pulley, said connectionincluding a follower and a defined path for the follower, said cammember I and pulley being arranged during normal movement of the doorwith the follower and path disposed to prevent rotation of the pulleyand hence relative movement between door and drive member, but with thefollower movable along said defined path when the door approaches theend of its travel to cause the pulley to rotate in a direction whichwould carry the drive member ahead of the door thereby slowing down thedoor to a position of rest, said follower and path also coming to restat least immediately after the door has come to rest in a positionenabling reverse rotation of the pulley, so that when the drive memberis moved backwards, the pulley will rotate in an opposite direction, thedoor will move away from rest and the cam member swing to move thefollower and path to a position once more locking the pulley againstrotation.

19. An anti-inertia device for a large slidable door moving relative toa fixed structure and having a flexible drive member adapted to be movedparallel with the door and have the door attached thereto, comprising apulley member pivoted on the door, the drive member making at least apartial loop around the pulley and tending to rotate the same thereby tocause relative movement between door and drive member, a cam memberpivotally mounted on the door with the pivot thereof spaced from thepull8 ley pivot and having a connection with said pulley, saidconnection including a follower and a defined path for the follower,said cam member and pulley being arranged during normal movement of thedoor with the follower and path disposed to prevent rotation of thepulley and hence relative movement between door and drive member, butwith the follower movable along said defined path when the doorapproaches the end of its travel to cause the pulley to rotate in adirection which would carry the drive member ahead of the door therebyslowing down the door, the said structure and cam member having meanscooperatively engaging as the said door approaches said end and rotatingsame a limited extent and said follower moving along said path duringsaid rotation in an are having thezp'ulley' pivot as its center whilemoving away from the cam member pivot, said path including anextensionengaged by the follower substantially at right angles with a line drawnthrough the follower and the cam member pivot whereby the cam member isprevented from further movement and the door is thus stopped, saiddevice being reversible to enable relative movement between drive memberand door when the drive member is driven in an opposite direction topermit the door to start from said stopped position without jerking.

20. In combination, a sliding door, an electrically operated drivingmechanism, a flexible drive member driven by said driving mechanism, afixed structure supporting said driving mechanism and having said doormovable relative thereto along a predetermined path, the flexible drivemember adapted to be connected to the door to drive the same, meanscontrolling said driving mechanism to start and stop the same, avariable coupling between the door and drive member permitting relativemovement between drive member and door, but only adjacent an end of saidpath, means for de-energizing said driving mechanism as the doorapproaches said path end, and means for enabling said relative movementat the end of the path, whereby when coming to rest or starting theinertia of the door will partially be absorbed, said coupling comprisinga pivoted pulley member, a cam member pivoted to the door and arrangedto rotate the pulley member, said means enabling such relative movementcomprising engaging means on the structure and cam which cooperate tomove the cam in one direction as the door approaches said end, and inthe opposite direction as the door leaves the said end.

21. In combination, a sliding door, an electrically operated drivingmechanism, a flexible drive member driven by said driving mechanism, afixed structure supporting said driving mechanism and having said doormovable relative thereto along a predetermined path, the flexible drivemember adapted to be connected to the door to drive the same, meanscontrolling said driving mechanism to start and stop the same, avariable coupling between the door and drive member permitting relativemovement between drive member and door, but only adjacent an end of saidpath, means for de-energizing said driving mechanism as the doorapproaches said path end, and means for enabling said relative movementat the end [of the path, whereby when coming to rest or starting theinertia of the door will be partially absorbed, said coupling comprisinga pivoted pulley member, :a cam member pivoted to the door and arrangedto rotate the pulley member, said means enabling such relative movementcomprising engaging means on the structure and cam which cooperate tomove the cam in one direction as the door approaches said end, and inthe opposite direction as the door leaves the said end, said cam andpulley having a slot and pin connection, the slot being of such shape tocarry the pin in a path about the pulley pivot but simultaneously in apath of varying distance from the cam pivot point.

22. A combination as described in claim 21 in which the slot also has aportion which prevents further movement of the pin relative to the campivot point except about the same whereby positively to define theposition of rest of said door.

WESTROPP ARMSTRONG.

References Cited in the file of this patent UNITED STATES PATENTS NumberNumber 20 Name Date Barker Sept. 25, 1923 Lemon June 14, 1927 ConnellyAug. 30, 1927 Edwards et a1 Mar. 6, 1928 Cloud Aug. 26, 1930 BancroftOct. 3, 1933 Konter July 17, 1934 Tamsitt June 4, 1935 Kahlifi June 22,1937 Lemon Mar. 21, 1939 Foster Mar. 26, 1940 Heginbotham et a1. Dec.10, 1940 Myers Jan. 4, 1949 Deakin Dec. 6, 1949 Rehwald Aug. 29, 1950Raque Oct. 17, 1950 Pianta et a1 Oct. 31, 1950

